CELLS

HYPOTHESIS

How many cells are in a typical fifth grader?

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BACKGROUND

In this modeling activity you will be working in groups of four. Your team will be making estimates of the number of cells in animals. There are many ways to make these estimates without actually counting the individual cells. Each team member may arrive at a different answer. The team should discuss how each answer was obtained and reach an consensus (agreement) for each animal. By doing this, your team can use the ideas and approaches that seem most reasonable and which result in a more accurate estimate.

MATERIALS

base ten blocks
calculator

PROCEDURE

1. Pretend that an ant is made of a single cell. Model this cell with a single base ten block.

2. Estimate how many blocks it takes to make an earthworm. Discuss this among the team members until you reach consensus. Record your team's answer in the chart.

ESTIMATED NUMBER OF "CELLS"
SUBJECT BASE TEN BLOCKS SALT CRYSTALS CELLS
ant


worm


mouse


goose


fifth grader


3. Reach a consensus among team members about how many blocks it takes to make a mouse and record your answer.

4. Reach a consensus among team members about how many blocks it takes to make a goose and record your answer.

5. Reach a consensus among team members about how many blocks it takes to make a fifth grader and record your answer.

6. Since an ant really is made of more than one cell, let's try this again starting with a multi-celled ant. Let's say that if you filled the space of a single base ten block with salt, you would need 50,000 salt crystals. So let the ant consist of 50,000 salt crystals.

7. Estimate how many salt crystals it would take to make up each of the other subjects.

8. The average size for a cell in the human body is 10 microns or 10 millionths of a meter. There are approximately 15,000 of these cells in one salt crystal. Estimate how many cells are in each of the subjects.

QUESTIONS

Name at least one way in which our model of the cells that make up animals is inaccurate:

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CONCLUSION

What did this activity teach us about cells?

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